1. Field of the Invention
The present invention relates to a device for retaining an element ejected by a pyrotechnic device when it is triggered. It can be applied especially to the retaining device of the rear igniter of a missile. More generally, it can be applied to any pyrotechnic device with rear ejection of elements such as the igniter, the explosive bolt, the booster, the skids or the lids.
During the phase of the firing of a pyrotechnic device such as the engine of a missile for example, the igniter of the engine is ejected at high speed backwards and has kinetic energy such that the ejection may cause very great harm to human beings and extensive damage to equipment.
2. Description of the Prior Art
To obtain protection from the elements that are thrown out, it may be planned to have a system external to the ammunition known as a system "on the launch pad". However, a system of this kind has many drawbacks. One example, among others, of drawbacks arises especially out of the fact that the launch pad cannot be too close to the rear of the device. Since they are relatively distant, the elements strike the launch pad with a kinetic energy that is all the greater. Consequently, the launch pad needs to have a sufficiently great mass for more material is needed to absorb the energy. This fact then leads to great complexity in the control servo-mechanisms of the launch pad. Furthermore, the relative distance of the launch pad does not always ensure that the elements thrown out will be captured in a reliable way.
Another approach may for example consist in eliminating the ejection. To prevent rear ejection from a pyrotechnic device, it is possible to ignite its engine from the front. In this case, the pyrotechnic elements are integrated during the assembling of the missile, entailing the risks associated with the handling and the in-plant testing of primed explosive elements.
The positioning of the igniter in the rear of the engine during the final phase of integration minimizes the pyrotechnical risks, especially risks in the plant, but leads to the ejection of the igniter at the firing stage. In addition to the flame effects, the structures located in the rear of the firing line receive, as mentioned here above, the projectiles that are constituted by the ejected elements. Given their high speed, which is greater than 100 m/s, these elements may possess kinetic energy of several hundreds of Joules. These projectiles may therefore cause major damage to neighboring structures or even cause injuries to operators, even if they are shielded, especially owing to the risks of ricochets that are impossible to control.
To prevent the risks associated with pyrotechnic devices of this kind during the firing stage while at the same time keeping the advantages associated with rear firing without using the launch pad to receive the ejected elements, it is necessary to capture these elements by means of a retaining device fixedly joined to the container of the device. In the case of application to a missile for example, the capturing device must in particular correspond to the following requirements:
the pyrotechnic elements should be captured and held captive during the phase of departure of the missile, namely for a time interval of about 0.2 seconds; PA1 the nozzle and the rear of the missile should be released from the missile at high speed, for example within less than 5 ms, to a distance of about 100 mm, but the movement should remain compatible with the templates chosen; PA1 the capturing device should not cause deterioration or disturbances that might lead to a defective launch, and furthermore the retaining forces should be compatible with the capacities of compensation of the servo-mechanisms of the missile-launching turret; PA1 the capturing device should be capable of withstanding the environmental stresses of the ammunition, namely those of the missile and container.